Exam 19: Work, heat, and the First Law of Thermodynamics

What is the net power that a person loses through radiation if her surface area is 1.20 m²,if her emissivity is 0.895,if her skin temperature is 300 K,and if she is in a room that is at a temperature of 17°C? The Stefan-Boltzmann constant is 5.670 × 10^-8 W/m² · K⁴.

If we use 67 W of power to heat 148 g of water,how long will it take to raise the temperature of the water from 15°C to 25°C? The specific heat of water is 4190 J/kg ∙ K.

A container of ideal gas has a movable frictionless piston.This container is placed in a very large water bath and slowly compressed so that the temperature of the gas remains constant and equal to the temperature of the water.Which of the following statements about this gas are true for this process? (There may be more than one correct choice.)

During an isothermal process,5.0 J of heat is removed from an ideal gas.How much work does the gas do during this process?

A chunk of ice (T = -20°C)is added to a thermally insulated container of cold water (T = 0°C).What happens in the container?

Two experimental runs are performed to determine the calorimetric properties of an alcohol that has a melting point of -10°C.In the first run,a 200-g cube of frozen alcohol,at the melting point,is added to 300 g of water at 20°C in a styrofoam container.When thermal equilibrium is reached,the alcohol-water solution is at a temperature of 5.0°C.In the second run,an identical cube of alcohol is added to 500 g of water at 20°C and the temperature at thermal equilibrium is 10°C.The specific heat of water is 4190 J/kg ∙ K.Assume that no heat is exchanged with the styrofoam container and with the surroundings.The heat of fusion of the alcohol is closest to

An ideal gas with γ = 1.67 is initially at 0°C in a volume of 10.0 L at a pressure of 1.00 atm.It is then expanded adiabatically to a volume of 10.4 L.What is the final temperature of the gas?

A person makes ice tea by adding ice to 1.8 kg of hot tea,initially at 80°C.How many kilograms of ice,initially at 0.00°C,are required to bring the mixture to 10°C? The heat of fusion of ice is 334 kJ/kg,and we can assume that tea has essentially the same thermal properties as water,so its specific heat is 4190 J/(kg ∙ K).

An adiabatic compression is performed on an ideal gas.The final pressure is equal to 0.560 times the initial pressure and the final volume equals 1.50 times the initial volume.What is the adiabatic constant for the gas?

The process shown in the T-V diagram in the figure is an

A solid concrete wall 4.0 m by 2.4 m and 30 cm thick,with a thermal conductivity of 1.3 W/(m ∙ K),separates a basement at 18°C from the ground outside at 6°C.Under steady state conditions,how much heat flows through the wall in one hour?

If 2.0 g of water at 0.00°C is to be vaporized,how much heat must be added to it? The specific heat of water is 1.0 cal/g ∙ K,its heat of fusion is 80 cal/g,and its heat of vaporization is 539 cal/g.

A cylinder contains 24.0 moles of an ideal gas at a temperature of 300 K.The gas is compressed at constant pressure until the final volume equals 0.63 times the initial volume.The molar heat capacity at constant volume of the gas is 24.0 J/mol · K and the ideal gas constant is R = 8.314 J/mol ∙ K.The change in the internal (thermal)energy of the gas is closest to

Two experimental runs are performed to determine the calorimetric properties of an alcohol that has a melting point of -10°C.In the first run,a 200-g cube of frozen alcohol,at the melting point,is added to 300 g of water at 20°C in a styrofoam container.When thermal equilibrium is reached,the alcohol-water solution is at a temperature of 5.0°C.In the second run,an identical cube of alcohol is added to 500 g of water at 20°C and the temperature at thermal equilibrium is 10°C.The specific heat of water is 4190 J/kg ∙ K.Assume that no heat is exchanged with the styrofoam container and with the surroundings.The specific heat of the alcohol is closest to

The temperature of an ideal gas in a sealed 0.40 container is reduced from 400 K to The final pressure of the gas is The molar heat capacity at constant volume of the gas is .The work done by the gas is closest to

When a gas undergoes an isothermal process,there is

A cube at 100.0°C radiates heat at a rate of 80.0 J/s.If the length of each side is cut in half,the rate at which it will now radiate is closest to

The filament in a light bulb has a diameter of 0.050 mm and an emissivity of 1.0.The temperature of the filament is 3000°C.What should be the length of the filament so it will radiate 60 W of power? The Stefan-Boltzmann constant is 5.670 × 10^-8 W/m² · K⁴.

A blacksmith is flattening a steel plate that measures 10 cm × 15 cm × 1 mm.He has heated the plate to 900 K.If the emissivity of the plate is 0.75,what is the total rate at which it radiates energy? The Stefan-Boltzmann constant is 5.670 × 10^-8 W/m² · K⁴.Ignore any heat it receives from the surroundings.

A heat conducting rod,1.40 m long,is made of an aluminum section that is 0.50 m long and a copper section that is long.Both sections have cross-sectional areas of The aluminum end and the copper end are maintained at temperatures of and respectively.The thermal conductivity of aluminum is 205 W/m ∙ K of copper is 385 W/m ∙ K.The rate at which heat is conducted in the rod is closest to